Risk and Prognostics of Second Primary Cancer After Prostate Radiation Therapy

INTRODUCTION

As overall survival in prostate cancer increases due to advances in early detection and management, there is a growing need to understand the long-term morbidity associated with treatment, including secondary tumors. The significance of developing radiation-associated secondary cancers in an elderly population remains unknown.

METHODS

Patients diagnosed with prostate cancer between 1975 and 2016 in one of 9 Surveillance, Epidemiology, and End Results registries were included in this study. Risk of second primary pelvic malignancies (SPPMs) were assessed with death as a competing risk using the Fine-Gray model. Time-varying Cox proportional hazard models were employed to analyze risk to overall mortality based on secondary tumor status.

RESULTS

A total of 569,167 primary prostate cancers were included in analysis with an average follow-up of 89 months. Among all prostate cancer patients, 4956 SPPMs were identified. After controlling for differences in age, year of diagnosis, and surgery at time of prostate cancer treatment, radiation receipt was associated with a significantly higher incidence of SPPMs (1.1% vs 1.8% at 25 years). Among those who received radiation during initial prostate cancer treatment (n = 195,415), developing an SPPM is significantly associated with worse survival (adjusted hazard ratio = 1.76), especially among younger patients (under age 63, adjusted hazard ratio = 2.36).

CONCLUSIONS

While developing a secondary malignancy carries a detrimental effect on overall survival, the absolute risk of developing such tumors is exceedingly low regardless of radiation treatment.

Oncologic Outcomes of Conventionally Fractionated, Hypofractionated, and Stereotactic Body Spot-Scanned Proton Radiation Therapy for Prostate Cancer: The Mayo Clinic Experience

PURPOSE/OBJECTIVE(S)

Spot/pencil beam scanned proton therapy is a relatively new technology with fundamental differences from double scattered or IMRT. We aimed to report the long-term oncologic outcomes of a contemporary prospective series of patients treated with spot-scanned proton therapy (SSPT).

MATERIALS/METHODS

An IRB-approved prospective registry identified patients with prostate cancer treated with proton therapy between January 2016 and December 2018. Descriptive statistics were calculated for all patients. Clinical, demographic, and treatment characteristics were gathered and analyzed. Kaplan-Meier curves were generated to estimate survival and recurrence rates. Outcomes assessed included 5-year overall survival (OS), 5-year local control (LC), biochemical failure (BF), regional and distant failures, and physician-reported adverse events (AEs). Biochemical failure was defined as rise in PSA ≥ 2.0 ng/mL above nadir PSA. Acute and chronic gastrointestinal (GI) and genitourinary (GU) grade 2+ and grade 3+ baseline-adjusted AEs were assigned using CTCAE v5.0. All failures were re-staged with PET C-11 or PSMA.

RESULTS

With a median follow up of 4.4 years (IQR 3.7 - 5), two hundred and eighty-six prostate cancer patients with a median age of 72 (IQR 67.5 - 77) were treated with spot-scanned proton radiation. The median Gleason grade group was 3 (IQR 2 - 4). The median pre-RT PSA was 6.9 ng/mL (IQR 4.3 - 10.5). Median T-stage was T1c. Nearly 64% of all patients were on androgen deprivation therapy at the time of initiating radiation treatment. The median total radiation dose was 79.2 Gy delivered over 44 fractions, 70 Gy over 28 fractions, and 38 Gy over 5 fractions for CF, HF, and SBRT regimens, respectively. The BF rate for all patients was 8.4%. The 5-year LC rates for CF, HF, and SBRT were 100% (95% CI: 100 - 100), 100% (95% CI: 100 - 100), and 97.3% (95% CI: 92.2 - 100), respectively (p = 0.07). Regional recurrences occurred in 12 (4.2%) patients: 8 (5.6%) treated with CF, 2 (2.1%) with HF, and 2 (4.3%) with SBRT (p = 0.62). Distant metastatic failures occurred in 12 patients (4.2%): 5 (3.5%) treated with CF, 7 (7.4%) with HF, and none with SBRT (0%) (p = 0.052). The 5-year OS for patients treated with CF, HF, and SBRT SSPT were 88.2% (95% CI: 81.8 - 95), 86.2% (95% CI: 77.6 - 95.6), and 97.2% (95% CI: 92 - 100), respectively (p = 0.1). Acute and chronic grade 2+ GI baseline-adjusted AEs occurred in 8 (2.8%) and 51 (17.8%) patients, respectively. Acute and chronic grade 3+ GI baseline-adjusted AEs occurred in 3 (1%) and 4 (1.4%) patients, respectively. Acute and chronic grade 2+ GU-related AEs were observed in 72 (25.2%) and 63 (22%) patients, respectively. Acute and chronic grade 3+ GU toxicity was observed in 3 (1%) and 6 (2.1%) patients, respectively.

CONCLUSION

Spot-scanned proton radiation therapy provides high local control rates and excellent oncologic outcomes across different fractionation schedules with low long-term AE rates.

Cardiopulmonary Toxicity Following Intensity-Modulated Proton Therapy (IMPT) Versus Intensity-Modulated Radiation Therapy (IMRT) for Stage III Non-Small Cell Lung Cancer

INTRODUCTION

Intensity-modulated proton therapy (IMPT) has the potential to reduce radiation dose to normal organs when compared to intensity-modulated radiation therapy (IMRT). We hypothesized that IMPT is associated with a reduced rate of cardiopulmonary toxicities in patients with Stage III NSCLC when compared with IMRT.

METHODS

We analyzed 163 consecutively treated patients with biopsy-proven, stage III NSCLC who received IMPT (n = 35, 21%) or IMRT (n = 128, 79%). Patient, tumor, and treatment characteristics were analyzed. Overall survival (OS), freedom-from distant metastasis (FFDM), freedom-from locoregional relapse (FFLR), and cardiopulmonary toxicities (CTCAE v5.0) were calculated using the Kaplan-Meier estimate. Univariate cox regressions were conducted for the final model.

RESULTS

Median follow-up of surviving patients was 25.5 (range, 4.6-58.1) months. Median RT dose was 60 (range, 45-72) Gy [RBE]. OS, FFDM, and FFLR were not different based on RT modality. IMPT provided significant dosimetric pulmonary and cardiac sparing when compared to IMRT. IMPT was associated with a reduced rate of grade more than or equal to 3 pneumonitis (HR 0.25, P = .04) and grade more than or equal to 3 cardiac events (HR 0.33, P = .08). Pre-treatment predicted diffusing capacity for carbon monoxide less than equal to 57% (HR 2.8, P = .04) and forced expiratory volume in the first second less than equal to 61% (HR 3.1, P = .03) were associated with an increased rate of grade more than or equal to 3 pneumonitis.

CONCLUSIONS

IMPT is associated with a reduced risk of clinically significant pneumonitis and cardiac events when compared with IMRT without compromising tumor control in stage III NSCLC. IMPT may provide a safer treatment option, particularly for high-risk patients with poor pretreatment pulmonary function.

A Phase II prospective study of hypofractionated proton therapy of prostate and pelvic lymph nodes: Acute effects on patient-reported quality of life

BACKGROUND

The objective of this study was to report acute changes in patient-reported quality of life (PRQOL) using the 26-item Expanded Prostate Index Composite (EPIC-26) questionnaire in a prospective study using hypofractionated intensity-modulated proton beam therapy (H-IMPT) targeting the prostate and the pelvic lymph nodes for high-risk or unfavorable intermediate-risk prostate cancer.

METHODS

Fifty-five patients were enrolled. H-IMPT consisted of 45 GyE to the pelvic lymph nodes and 67.5 GyE to the prostate and seminal vesicles in 25 fractions. PRQOL was assessed with the urinary incontinence (UI), urinary irritative/obstructive symptoms (UO), and bowel function (BF) domains of EPIC-26 questionnaire. Mean changes in domain scores were analyzed from pretreatment to the end of treatment and 3 months posttreatment. A clinically meaningful change (or minimum important change) was defined as a score change > 50% of the baseline standard deviation.

RESULTS

The mean scores of UO, UI, and BF at baseline were 84.6, 91.1, and 95.3, respectively. At the end of treatment, there were statistically significant and clinically meaningful declines in UO and BF scores (-13.5 and -2.3, respectively), while the decline in UI score was statistically significant but not clinically meaningful (-13.7). A clinically meaningful decline in UO, UI, and BF scores occurred in 53.5%, 22.7%, and 73.2% of the patients, respectively. At 3 months posttreatment, all three mean scores showed an improvement, with fewer patients having a clinically meaningful decline in UO, UI, and BF scores (18.4%, 20.5%, and 45.0%, respectively). There was no significant reduction in the mean UO and UI scores compared to baseline, although the mean BF score remained lower than baseline and the difference was clinically meaningful.

CONCLUSIONS

UO, UI, and BF scores of PRQOL declined at the end of H-IMPT. UO and UI scores showed improvement at 3 months posttreatment and were similar to the baseline scores. However, BF score remained lower at 3 months posttreatment with a clinically meaningful decline.

Patient vs. Caregiver: Correlation and Differences in Pediatric Quality of Life (PedsQL) Using a Prospective Registry in a Large-Volume, Multi-Site Practice

PURPOSE

Patient reported outcomes (PROs) provide quality of life (QOL) data during and after radiation. When pediatric patients are unable to complete PROs, it is unknown whether caregiver responses are an accurate surrogate. We assessed whether caregiver scores for the Pediatric Quality of Life Inventory (PedsQL) Core and Brain Tumor Module questionnaires can substitute for missing child scores.

METHODS AND MATERIALS

From 2016-2018, pediatric patients treated with radiation were followed in a prospective, institutional registry. Child and caregiver Core and Tumor PedsQL surveys were obtained at pre-treatment, end of treatment, and in regular follow-up. The differences between the two scores at each time point were quantified using a linear mixed-model (LMM) while the level of agreement was estimated with intraclass correlation (ICC). An ICC 95% confidence interval lower limit exceeding 0.75 was considered an acceptable threshold for using caregiver scores as imputed values for missing child scores.

RESULTS

Ninety-one children completed 403 surveys. Caregivers underestimated QOL scores at baseline, but not at end of treatment or any follow-up time. The PedsQL Core total score had an ICC of 0.88 (95% CI: 0.81-0.92), while the emotional, physical, school, and social function subdomain scores were 0.81 (0.72-0.88), 0.72 (0.58-0.82), 0.79 (0.68-0.86), and 0.75 (0.62-0.83), respectively. The Tumor total score ICC was 0.91 (0.85, 0.94), and each of the subdomains (cognitive problems, communication, movement and balance, nausea, pain and hurt, perceived physical appearance, procedural anxiety, treatment anxiety, and worry) had ICC lower bound 95% CI ≥ 0.75 except for communication (0.83, 0.74-0.89). Bland-Altman analysis demonstrated no visual change in discrepancy between child and caregiver estimates as overall QOL improved.

CONCLUSION

Agreement between child and caregiver-reported QOL was generally strong in the acute period after radiation, implying that caregiver scores may be imputed for child scores in future protocols and analyses of pediatric QOL.

Dose-volume histogram parameters and patient-reported EPIC-Bowel domain in prostate cancer proton therapy

Purpose

To analyze rectal dose and changes in quality of life (QOL) measured with the Expanded Prostate and Cancer Index Composite (EPIC) bowel domain in patients being treated for prostate cancer with curative-intent proton beam therapy (PBT) within a large single-institution prospective registry.

Materials and Methods

Data was collected from 243 patients with localized prostate cancer treated with PBT from 2016 to 2018. The EPIC survey was administered at baseline, end-of-treatment, 3, 6, and 12 months, then annually. Dose-volume histogram (DVH) parameters for the rectum were computed, and rectal dose was analyzed using BED (α/β = 3), EQD_2Gy, and total dose. Repeated measures mixed models were implemented to determine the effect of patient, clinical, and treatment factors (including DVH) on patient-reported bowel symptom burden (EPIC-Bowel).

Results

Treatment overall resulted in changes in EPIC-Bowel scores (baseline score = 93.7), most notably at end-of-treatment (90.6) and 12 months (89.7). However, they returned to baseline at 36 months (92.9). On multivariate modeling, rectal BED D₂₅ (Gy) ≥23% was significantly associated with decline in QOL scores measuring bother (p < 0.01; 4.06 points different).

Conclusion

Rectal doses, specifically BED D₂₅ (Gy) ≥23%, are significantly associated with decline in bowel bother-related QOL in patients undergoing definitive radiotherapy for localized prostate cancer. This study demonstrates BED as an independent predictor of bowel QOL across dose fractionations of PBT.

Assessing concordance between patient-reported and investigator-reported CTCAE after proton beam therapy for prostate cancer

PURPOSE

We report acute patient-reported outcomes using CTCAE (PRO-CTCAE) of proton beam radiotherapy for high-risk or unfavorable intermediate-risk prostate cancer in a prospective clinical trial. PRO-CTCAE were correlated with investigator reported-CTCAE (IR-CTCAE) to assess the degree of concordance.

METHODS AND MATERIALS

11 PRO-CTCAE questions assessed gastrointestinal (GI), genitourinary (GU), or erectile function side effects. The correlation scheme between PRO-CTCAE and IR-CTCAE was independently developed by two physicians. Analyses of PRO-CTCAE and IR-CTCAE were conducted using both descriptive terms and the converted grade scores. The Kappa statistic described the degree of concordance.

RESULTS

55 patients were included. IR-CTCAE underestimated diarrhea compared to PRO-CTCAE at the end of treatment (EOT), with a 28% rate of underestimation (11% by ≥ 2 toxicity grades). Similarly, urinary tract pain was underestimated in 45% of cases (17% by ≥ 2 grades) at EOT. Differences were less pronounced at baseline or 3 months after radiotherapy. The incidence of urinary urgency and frequency tended to be overestimated prior to treatment (36% and 24%, respectively) but underestimated at EOT (35% and 31%, respectively). The degree of interference with daily activities was consistently overestimated by investigators (45%-85%). Finally, erectile dysfunction showed a 36-56% rate of discordance by ≥ 2 toxicity grades.

CONCLUSIONS

Our study shows a low agreement between IR-CTCAE and PRO-CTCAE in the setting of proton therapy for prostate cancer. Compared to patient-reported outcomes, physicians underestimated the frequency and severity of urinary symptoms and diarrhea at the end of treatment. Continued use of PROs should be strongly encouraged.

Biologically Effective Dose and Rectal Bleeding in Definitive Proton Therapy for Prostate Cancer

Purpose and Objectives

With increasing use of hypofractionation and extreme hypofractionation for prostate cancer, rectal dose-volume histogram (DVH) parameters that apply across dose fractionations may be helpful for treatment planning in clinical practice. We present an exploratory analysis of biologically effective rectal dose (BED) and equivalent rectal dose in 2 Gy fractions (EQD2) for rectal bleeding in patients treated with proton therapy across dose fractionations.

Materials and Methods

From 2016 to 2018, 243 patients with prostate cancer were treated with definitive proton therapy. Rectal DVH parameters were obtained from treatment plans, and rectal bleeding events were recorded. The BED and EQD2 transformations were applied to each rectal DVH parameter. Univariate analysis using logistic regression was used to determine DVH parameters that were significant predictors of grade ≥ 2 rectal bleeding. Youden index was used to determine optimum cutoffs for clinically meaningful DVH constraints. Stepwise model-selection criteria were then applied to fit a “best” multivariate logistic model for predicting Common Terminology Criteria for Adverse Events grade ≥ 2 rectal bleeding.

Results

Conventional fractionation, hypofractionation, and extreme hypofractionation were prescribed to 117 (48%), 84 (34%), and 42 (17.3%) patients, respectively. With a median follow-up of 20 (2.5-40) months, 10 (4.1%) patients experienced rectal bleeding. On univariate analysis, multiple rectal DVH parameters were significantly associated with rectal bleeding across BED, EQD2, and nominal doses. The BED volume receiving 55 Gy > 13.91% was found to be statistically and clinically significant. The BED volume receiving 55 Gy remained statistically significant for an association with rectal bleeding in the multivariate model (odds ratio, 9.81; 95% confidence interval, 2.4-40.5; P = .002).

Conclusion

In patients undergoing definitive proton therapy for prostate cancer, dose to the rectum and volume of the rectum receiving the dose were significantly associated with rectal bleeding across conventional fractionation, hypofractionation, and extreme hypofractionation when using BED and EQD2 transformations.

Exploratory Investigation of Dose-Linear Energy Transfer (LET) Volume Histogram (DLVH) for Adverse Events Study in Intensity Modulated Proton Therapy (IMPT)

PURPOSE

We proposed a novel tool-a dose linear energy transfer (LET)-volume histogram (DLVH)-and performed an exploratory study to investigate rectal bleeding in prostate cancer treated with intensity modulated proton therapy.

METHODS AND MATERIALS

The DLVH was constructed with dose and LET as 2 axes, and the normalized volume of the structure was contoured in the dose-LET plane as isovolume lines. We defined the DLVH index, DLv%(d,l) (ie, v% of the structure) to have a dose of ≥d Gy and an LET of ≥l keV/μm, similar to the dose-volume histogram index Dv%. Nine patients with prostate cancer with rectal bleeding (Common Terminology Criteria for Adverse Events grade ≥2) were included as the adverse event group, and 48 patients with no complications were considered the control group. A P value map was constructed by comparison of the DLVH indices of all patients between the 2 groups using the Mann-Whitney U test. Dose-LET volume constraints (DLVCs) were derived based on the P value map with a manual selection procedure facilitated by Spearman's correlation tests. The obtained DLVCs were further cross-validated using a multivariate support vector machine (SVM)-based normal tissue complication probability (NTCP) model with an independent testing data set composed of 8 adverse event and 13 control patients.

RESULTS

We extracted 2 DLVC constraints. One DLVC was obtained, Vdose/LETboundary:2.5keVμmat 75 Gy to 3.2keVμmat8.65Gy <1.27% (DLVC1), revealing a high LET volume effect. The second DLVC, V(72.2Gy,0keVμm) < 2.23% (DVLC2), revealed a high dose volume effect. The SVM-based NTCP model with 2 DLVCs provided slightly superior performance than using dose only, with an area under the curve of 0.798 versus 0.779 for the testing data set.

CONCLUSIONS

Our results demonstrated the importance of rectal "hot spots" in both high LET (DLVC1) and high dose (DLVC2) in inducing rectal bleeding. The SVM-based NTCP model confirmed the derived DLVCs as good predictors for rectal bleeding when intensity modulated proton therapy is used to treat prostate cancer.

Technical Note: Multiple energy extraction techniques for synchrotron-based proton delivery systems may exacerbate motion interplay effects in lung cancer treatments

PURPOSE

The multiple energy extraction (MEE) delivery technique for synchrotron-based proton delivery systems reduces beam delivery time by decelerating the beam multiple times during one accelerator spill, but this might cause additional plan quality degradation due to intrafractional motion. We seek to determine whether MEE causes significantly different plan quality degradation compared to single energy extraction (SEE) for lung cancer treatments due to the interplay effect.

METHODS

Ten lung cancer patients treated with IMPT at our institution were nonrandomly sampled based on a representative range of tumor motion amplitudes, tumor volumes, and respiratory periods. Dose-volume histogram (DVH) indices from single-fraction SEE and MEE four-dimensional (4D) dynamic dose distributions were compared using the Wilcoxon signed-rank test. Distributions of monitor units (MU) to breathing phases were investigated for features associated with plan quality degradation. SEE and MEE DVH indices were compared in fractionated deliveries of the worst-case patient treatment scenario to evaluate the impact of fractionation.

RESULTS

There were no clinically significant differences in target mean dose, target dose conformity, or dose to organs-at-risk between SEE and MEE in single-fraction delivery. Three patients had significantly worse dose homogeneity with MEE compared to SEE (single-fraction mean D_5% -D_95% increased by up to 9.6% of prescription dose), and plots of MU distribution to breathing phases showed synchronization patterns with MEE but not SEE. However, after 30 fractions the patient in the worst-case scenario had clinically acceptable target dose homogeneity and coverage with MEE (mean D_5% -D_95% increased by 1% compared to SEE).

CONCLUSIONS

For some patients with breathing periods close to the mean spill duration, MEE resulted in significantly worse single-fraction target dose homogeneity compared to SEE due to the interplay effect. However, this was mitigated by fractionation, and target dose homogeneity and coverage were clinically acceptable after 30 fractions with MEE.

Consensus Statement on Proton Therapy for Prostate Cancer

Proton therapy is a promising but controversial treatment in the management of prostate cancer. Despite its dosimetric advantages when compared with photon radiation therapy, its increased cost to patients and insurers has raised questions regarding its value. Multiple prospective and retrospective studies have been published documenting the efficacy and safety of proton therapy for patients with localized prostate cancer and for patients requiring adjuvant or salvage pelvic radiation after surgery. The Particle Therapy Co-Operative Group (PTCOG) Genitourinary Subcommittee intends to address current proton therapy indications, advantages, disadvantages, and cost effectiveness. We will also discuss the current landscape of clinical trials. This consensus report can be used to guide clinical practice and research directions.

Proton beam radiotherapy for patients with early-stage and advanced lung cancer: a narrative review with contemporary clinical recommendations

Although lung cancer rates are decreasing nationally, lung cancer remains the leading cause of cancer related death. Despite advancements in treatment and technology, overall survival (OS) for lung cancer remains poor. Proton beam therapy (PBT) is an advanced radiation therapy (RT) modality for treatment of lung cancer with the potential to achieve dose escalation to tumor while sparing critical structures due to higher target conformality. In early and late-stage non-small cell lung cancer (NSCLC), dosimetric studies demonstrated reduced doses to organs at risk (OARs) such as the lung, spinal cord, and heart, and clinical studies report limited toxicities with PBT, including hypofractionated regimens. In limited-stage SCLC, studies showed that regimens chemo RT including PBT were well tolerated, which may help optimize clinical outcomes. Improved toxicity profiles may be beneficial in post-operative radiotherapy, for which initial dosimetric and clinical data are encouraging. Sparing of OARs may also increase the proportion of patients able to complete reirradiation for recurrent disease. However, there are various challenges of using PBT including a higher financial burden on healthcare and limited data supporting its cost-effectiveness. Further studies are needed to identify subgroups that benefit from PBT based on prognostic factors, and to evaluate PBT combined with immunotherapy, in order to elucidate the benefit that PBT may offer future lung cancer patients.

Intensity-modulated proton therapy (IMPT) interplay effect evaluation of asymmetric breathing with simultaneous uncertainty considerations in patients with non-small cell lung cancer

PURPOSE

Intensity-modulated proton therapy (IMPT) is sensitive to uncertainties from patient setup and proton beam range, as well as interplay effect. In addition, respiratory motion may vary from cycle to cycle, and also from day to day. These uncertainties can severely degrade the original plan quality and potentially affect patient's outcome. In this work, we developed a new tool to comprehensively consider the impact of all these uncertainties and provide plan robustness evaluation under them.

METHODS

We developed a comprehensive plan robustness evaluation tool that considered both uncertainties from patient setup and proton beam range, as well as respiratory motion simultaneously. To mimic patients' respiratory motion, the time spent in each phase was randomly sampled based on patient-specific breathing pattern parameters as acquired during the four-dimensional (4D)-computed tomography (CT) simulation. Spots were then assigned to one specific phase according to the temporal relationship between spot delivery sequence and patients' respiratory motion. Dose in each phase was calculated by summing contributions from all the spots delivered in that phase. The final 4D dynamic dose was obtained by deforming all doses in each phase to the maximum exhalation phase. Three hundred (300) scenarios (10 different breathing patterns with 30 different setup and range uncertainty scenario combinations) were calculated for each plan. The dose-volume histograms (DVHs) band method was used to assess plan robustness. Benchmarking the tool as an application's example, we compared plan robustness under both three-dimensional (3D) and 4D robustly optimized IMPT plans for 10 nonrandomly selected patients with non-small cell lung cancer.

RESULTS

The developed comprehensive plan robustness tool had been successfully applied to compare the plan robustness between 3D and 4D robustly optimized IMPT plans for 10 lung cancer patients. In the presence of interplay effect with uncertainties considered simultaneously, 4D robustly optimized plans provided significantly better CTV coverage (D_95% , P = 0.002), CTV homogeneity (D_5% -D_95% , P = 0.002) with less target hot spots (D_5% , P = 0.002), and target coverage robustness (CTV D_95% bandwidth, P = 0.004) compared to 3D robustly optimized plans. Superior dose sparing of normal lung (lung D_mean , P = 0.020) favoring 4D plans and comparable normal tissue sparing including esophagus, heart, and spinal cord for both 3D and 4D plans were observed. The calculation time for all patients included in this study was 11.4 ± 2.6 min.

CONCLUSION

A comprehensive plan robustness evaluation tool was successfully developed and benchmarked for plan robustness evaluation in the presence of interplay effect, setup and range uncertainties. The very high efficiency of this tool marks its clinical adaptation, highly practical and versatile nature, including possible real-time intra-fractional interplay effect evaluation as a potential application for future use.

Clinical evaluation of fitness to drive in patients with brain metastases

Background

Guidelines to provide recommendations about driving restrictions for patients with brain metastases are lacking. We aim to determine whether clinical neurologic examination is sufficient to predict suitability to drive in these patients by comparison with an occupational therapy driving assessment (OTDA).

Methods

We prospectively evaluated the concordance between neurology assessment of suitability to drive (pass/fail) and OTDA in 41 individuals with brain metastases. Neuro-oncology evaluation included an interview and neurological examination. Participants subsequently underwent OTDA during which a battery of objective measures of visual, cognitive, and motor skills related to driving was administered.

Results

The mean age of patients who failed OTDA was age 68.9 years vs 59.3 years in the group members who passed (P = .0046). The sensitivity of the neurology assessment to predict driving fitness compared with OTDA was 16.1% and the specificity 90%. The 31 patients who failed OTDA were more likely to fail Vision Coach, Montreal Cognitive Assessment, and Trail Making B tests.

Conclusions

There was poor association between the assessment of suitability to drive by neurologists and the outcome of the OTDA in patients with brain metastases. Subtle deficits that may impair the ability to drive safely may not be evident on neurologic examination. The positive predictive value was high to predict OTDA failure. Age could be a factor affecting OTDA performance. The results raise questions about the choice of assessments in making recommendations about driving fitness in people with brain metastases. OTDA should be strongly considered in patients with brain metastases who wish to continue driving.

Technical Note: Treatment planning system (TPS) approximations matter - comparing intensity-modulated proton therapy (IMPT) plan quality and robustness between a commercial and an in-house developed TPS for nonsmall cell lung cancer (NSCLC)

PURPOSE

Approximate dose calculation methods were used in the nominal dose distribution and the perturbed dose distributions due to uncertainties in a commercial treatment planning system (CTPS) for robust optimization in intensity-modulated proton therapy (IMPT). We aimed to investigate whether the approximations influence plan quality, robustness, and interplay effect of the resulting IMPT plans for the treatment of locally advanced lung cancer patients.

MATERIALS AND METHODS

Ten consecutively treated locally advanced nonsmall cell lung cancer (NSCLC) patients were selected. Two IMPT plans were created for each patient using our in-house developed TPS, named "Solo," and also the CTPS, Eclipse^TM (Varian Medical Systems, Palo Alto, CA, USA), respectively. The plans were designed to deliver prescription doses to internal target volumes (ITV) drawn by a physician on averaged four-dimensional computed tomography (4D-CT). Solo plans were imported back to CTPS, and recalculated in CTPS for fair comparison. Both plans were further verified for each patient by recalculating doses in the inhalation and exhalation phases to ensure that all plans met clinical requirements. Plan robustness was quantified on all phases using dose-volume-histograms (DVH) indices in the worst-case scenario. The interplay effect was evaluated for every plan using an in-house developed software, which randomized starting phases of each field per fraction and accumulated dose in the exhalation phase based on the patient's breathing motion pattern and the proton spot delivery in a time-dependent fashion. DVH indices were compared using Wilcoxon rank-sum test.

RESULTS

Compared to the plans generated using CTPS on the averaged CT, Solo plans had significantly better target dose coverage and homogeneity (normalized by the prescription dose) in the worst-case scenario [ITV D_95% : 98.04% vs 96.28%, Solo vs CTPS, P = 0.020; ITV D_5% -D_95% : 7.20% vs 9.03%, P = 0.049] while all DVH indices were comparable in the nominal scenario. On the inhalation phase, Solo plans had better target dose coverage and cord D_max in the nominal scenario [ITV D_95% : 99.36% vs 98.45%, Solo vs CTPS, P = 0.014; cord D_max : 20.07 vs 23.71 Gy(RBE), P = 0.027] with better target coverage and cord D_max in the worst-case scenario [ITV D_95% : 97.89% vs 96.47%, Solo vs CTPS, P = 0.037; cord D_max : 24.57 vs 28.14 Gy(RBE), P = 0.037]. On the exhalation phase, similar phenomena were observed in the nominal scenario [ITV D_95% : 99.63% vs 98.87%, Solo vs CTPS, P = 0.037; cord D_max : 19.67 vs 23.66 Gy(RBE), P = 0.039] and in the worst-case scenario [ITV D_95% : 98.20% vs 96.74%, Solo vs CTPS, P = 0.027; cord D_max : 23.47 vs 27.93 Gy(RBE), P = 0.027]. In terms of interplay effect, plans generated by Solo had significantly better target dose coverage and homogeneity, less hot spots, and lower esophageal D_mean , and cord D_max [ITV D_95% : 101.81% vs 98.68%, Solo vs CTPS, P = 0.002; ITV D_5% -D_95% : 2.94% vs 7.51%, P = 0.002; cord D_max : 18.87 vs 22.29 Gy(RBE), P = 0.014].

CONCLUSIONS

Solo-generated IMPT plans provide improved cord sparing, better target robustness in all considered phases, and reduced interplay effect compared with CTPS. Consequently, the approximation methods currently used in commercial TPS programs may have space for improvement in generating optimal IMPT plans for patient cases with locally advanced lung cancer.

Early Outcomes of Patients With Locally Advanced Non-small Cell Lung Cancer Treated With Intensity-Modulated Proton Therapy Versus Intensity-Modulated Radiation Therapy: The Mayo Clinic Experience

Purpose

There are very little data available comparing outcomes of intensity-modulated proton therapy (IMPT) to intensity-modulated radiation therapy (IMRT) in patients with locally advanced NSCLC (LA-NSCLC).

Methods

Seventy-nine consecutively treated patients with LA-NSCLC underwent definitive IMPT (n = 33 [42%]) or IMRT (n = 46 [58%]) from 2016 to 2018 at our institution. Survival rates were calculated using the Kaplan-Meier method and compared with the log-rank test. Acute and subacute toxicities were graded based on Common Terminology Criteria for Adverse Events, version 4.03.

Results

Median follow-up was 10.5 months (range, 1-27) for all surviving patients. Most were stage III (80%), received median radiation therapy (RT) dose of 60 Gy (range, 45-72), and had concurrent chemotherapy (65%). At baseline, the IMPT cohort was older (76 vs 69 years, P < .01), were more likely to be oxygen-dependent (18 vs 2%, P = .02), and more often received reirradiation (27 vs 9%, P = .04) than their IMRT counterparts. At 1 year, the IMPT and IMRT cohorts had similar overall survival (68 vs 65%, P = .87), freedom from distant metastasis (71 vs 68%, P = .58), and freedom from locoregional recurrence (86 vs 69%, P = .11), respectively. On multivariate analyses, poorer pulmonary function and older age were associated with grade +3 toxicities during and 3 months after RT, respectively (both P ≤ .02). Only 5 (15%) IMPT and 4 (9%) IMRT patients experienced grade 3 or 4 toxicities 3 months after RT (P = .47). There was 1 treatment-related death from radiation pneumonitis 6 months after IMRT in a patient with idiopathic pulmonary fibrosis.

Conclusions

Compared with IMRT, our early experience suggests that IMPT resulted in similar outcomes in a frailer population of LA-NSCLC who were more often being reirradiated. The role of IMPT remains to be defined prospectively.

Small-spot intensity-modulated proton therapy and volumetric-modulated arc therapies for patients with locally advanced non-small-cell lung cancer: A dosimetric comparative study

Purpose

To compare dosimetric performance of volumetric‐modulated arc therapy (VMAT) and small‐spot intensity‐modulated proton therapy for stage III non‐small‐cell lung cancer (NSCLC).

Methods and Materials

A total of 24 NSCLC patients were retrospectively reviewed; 12 patients received intensity‐modulated proton therapy (IMPT) and the remaining 12 received VMAT. Both plans were generated by delivering prescription doses to clinical target volumes (CTV) on averaged 4D‐CTs. The dose‐volume‐histograms (DVH) band method was used to quantify plan robustness. Software was developed to evaluate interplay effects with randomized starting phases of each field per fraction. DVH indices were compared using Wilcoxon rank sum test.

Results

Compared with VMAT, IMPT delivered significantly lower cord D_max, heart D_mean, and lung V_5 Gy[RBE] with comparable CTV dose homogeneity, and protection of other OARs. In terms of plan robustness, the IMPT plans were statistically better than VMAT plans in heart D_mean, but were statistically worse in CTV dose coverage, cord D_max, lung D_mean, and V_5 Gy[RBE]. Other DVH indices were comparable. The IMPT plans still met the standard clinical requirements with interplay effects considered.

Conclusions

Small‐spot IMPT improves cord, heart, and lung sparing compared to VMAT and achieves clinically acceptable plan robustness at least for the patients included in this study with motion amplitude less than 11 mm. Our study supports the usage of IMPT to treat some lung cancer patients.

Prophylactic Cranial Irradiation for Extensive Small-Cell Lung Cancer

Small-cell lung cancer (SCLC) has a high predilection for metastasizing to the brain after chemotherapy. This has been blamed on the blood-brain barrier, which prevents chemotherapy from penetrating into the brain, thus creating a sanctuary site. It has been estimated that up to three quarters of patients with SCLC will eventually develop brain metastases. This led investigators to administer prophylactic cranial irradiation (PCI) to decrease this risk. Several trials were performed in patients with SCLC after initial therapy (chemotherapy with or without thoracic radiotherapy) that compared the outcomes of PCI versus no PCI. Early trials generally found that PCI significantly decreased the risk of brain metastases but did not significantly improve survival. These trials were re-evaluated in two larger meta-analyses that included patients with either limited-stage SCLC or extensive-stage SCLC (ESCLC). Both meta-analyses reported that PCI significantly decreased brain metastases and improved survival in patients who had a complete response following initial therapy. These studies were performed before the advent of modern imaging with computed tomography or magnetic resonance imaging (MRI). There have been two modern trials of PCI versus no PCI in patients with ESCLC and both found that PCI decreases brain metastases. The first did not include brain MRI before registration and found that PCI improved survival, whereas the second study did include MRI before registration and at frequent intervals thereafter. That trial found that PCI did not confer a survival advantage. This review will examine the evidence and provide recommendations regarding the role of PCI for patients with ESCLC.

Photon and Proton Radiation Therapy Utilization in a Population of More Than 100 Million Commercially Insured Patients

PURPOSE

To characterize the changes in the use of radiation therapy (RT), specifically proton beam radiation therapy (PBRT), among adult and pediatric patients over a 11-year period in a very large population of insured patients.

METHODS AND MATERIALS

We conducted a retrospective analysis of the OptumLabs Data Warehouse claims database of more than 100 million insured US enrollees. Descriptive analyses were undertaken to evaluate the characteristics of patients receiving RT from 2002 to 2012.

RESULTS

There were 474,533 patients treated with RT from 2002 to 2012. The percentage of patients treated with 3-dimensional conformal radiation therapy, 2-dimensional RT/brachytherapy, intensity modulated radiation therapy (IMRT), stereotactic body radiation therapy (SBRT), and PBRT was 34.5%, 63.4%, 2.1%, 0.0%, and 0.1% and 40.4%, 36.0%, 21.9%, 1.1%, and 0.6% in 2002 and 2012, respectively. The greatest increase in utilization was of IMRT for prostate cancer, growing from 3.5% to 64.0%. For non-prostate cancer adults, IMRT use grew from 1.7% to 16.4%. For children, PBRT utilization increased from 0.3% to 9.7%. For prostate cancer patients, PBRT increased from 0.0% to 2.6%. For all patients, advanced technology (SBRT and PBRT) use was very low at <2%, versus 22% for IMRT.

CONCLUSIONS

This is the largest and most geographically diverse description of RT utilization. Proton beam RT utilization remains very low and has had little impact on overall RT utilization compared with IMRT. The largest shift has occurred in IMRT for prostate cancer. Our findings indicate that overall utilization of proton therapy has been low and that its use has likely had little impact on national expenditures on cancer care in the current environment.

Pediatric Metastatic Odontogenic Ghost Cell Carcinoma: A Multimodal Treatment Approach

Odontogenic ghost cell carcinoma (OGCC) is a rare and aggressive tumor wherein optimal treatment remains uncertain. We report the first pediatric metastatic OGCC case treated with multimodal therapy: surgery, adjuvant chemoradiation, and adjuvant immunotherapy. Adjuvant therapy was utilized due to locally advanced disease with pathologic features indicative of high recurrence risk. This multimodal approach was modeled after management of primary head and neck cancer, where adjuvant chemoradiation and immunotherapy are associated with improved outcomes. Our patient is alive and disease free at 14 months indicating a potentially positive role for multimodal therapy in the management of OGCC.

Early Outcome of Prostate Intensity Modulated Radiation Therapy (IMRT) Incorporating a Simultaneous Intra-Prostatic MRI Directed Boost

This study assessed the feasibility and outcomes of treating prostate cancer with intensity modulated radiotherapy (IMRT) incorporating a Magnetic Resonance Imaging (MRI) directed boost. Seventy-eight men received IMRT for localized prostate cancer. The entire prostate received 77.4Gy in 43 fractions and simultaneous intra-prostatic boosts (SIB) of 83Gy were administered to increase the dose to the MRI identified malignancy. In 16 (21%) patients, the MRI didn't detect a neoplasm and these patients received an SIB of 81Gy to the posterior prostate. Androgen Deprivation Therapy (ADT) was also administered to 32 (41%) patients. The 3-year rates of biochemical control, local control, distant control, and survival were 92%, 98%, 95%, and 95% respectively. While grade 1-2 toxicities were common, there were only 2 patients who suffered grade 3 toxicity. These patients developed strictures which were dilated resulting in improvement in symptoms such that both had grade 1-2 toxicity at last follow up examination. The results of this program of IMRT incorporating a MRI directed intra-prostatic boost suggest this technique is feasible and well tolerated. This technique appears to shift the therapeutic index favorably by boosting the malignancy to the highest dose without increasing the doses administered to the bladder and rectum.

Validation of EORTC prognostic factors for adults with low-grade glioma: a report using intergroup 86-72-51

PURPOSE

A prognostic index for survival was constructed and validated from patient data from two European Organisation for Research and Treatment of Cancer (EORTC) radiation trials for low-grade glioma (LGG). We sought to independently validate this prognostic index with a separate prospectively collected data set (Intergroup 86-72-51).

METHODS AND MATERIALS

Two hundred three patients were treated in a North Central Cancer Treatment Group-led trial that randomized patients with supratentorial LGG to 50.4 or 64.8 Gy. Risk factors from the EORTC prognostic index were analyzed for prognostic value: histology, tumor size, neurologic deficit, age, and tumor crossing the midline. The high-risk group was defined as patients with more than two risk factors. In addition, the Mini Mental Status Examination (MMSE) score, extent of surgical resection, and 1p19q status were also analyzed for prognostic value.

RESULTS

On univariate analysis, the following were statistically significant (p<0.05) detrimental factors for both progression-free survival (PFS) and overall survival (OS): astrocytoma histology, tumor size, and less than total resection. A Mini Mental Status Examination score of more than 26 was a favorable prognostic factor. Multivariate analysis showed that tumor size and MMSE score were significant predictors of OS whereas tumor size, astrocytoma histology, and MMSE score were significant predictors of PFS. Analyzing by the EORTC risk groups, we found that the low-risk group had significantly better median OS (10.8 years vs. 3.9 years, p<0.0001) and PFS (6.2 years vs. 1.9 years, p<0.0001) than the high-risk group. The 1p19q status was available in 66 patients. Co-deletion of 1p19q was a favorable prognostic factor for OS vs. one or no deletion (median OS, 12.6 years vs. 7.2 years; p=0.03).

CONCLUSIONS

Although the low-risk group as defined by EORTC criteria had a superior PFS and OS to the high-risk group, this is primarily because of the influence of histology and tumor size. Co-deletion of 1p19q is a prognostic factor. Future studies are needed to develop a more refined prognostic system that combines clinical prognostic features with more robust molecular and genetic data.